A patch implementing a relaxed termination constraint is at
http://www.soi.city.ac.uk/~ross/instance-termination.patch
Here is the description:
With -fglasgow-exts but not -fallow-undecidable-instances, GHC 6.4
requires that instances be of the following form:
(1) each assertion
Ross, and Martin,
Thanks! But I'm not certain that your fix is correct. Let's ask
Martin. I've added comments below.
| -Original Message-
| From: [EMAIL PROTECTED]
[mailto:glasgow-haskell-users-
| [EMAIL PROTECTED] On Behalf Of Ross Paterson
| Sent: 06 February 2006 11:36
| To: Simon
On Mon, Feb 06, 2006 at 11:53:17AM -, Simon Peyton-Jones wrote:
Thanks! But I'm not certain that your fix is correct. Let's ask
Martin. I've added comments below.
[...]
Yes, (1-GHC) certainly contradicts the FD paper that Martin and I wrote.
I think (1) should be:
(1-fixed)
On Mon, Feb 06, 2006 at 12:07:54PM +, Ross Paterson wrote:
On Mon, Feb 06, 2006 at 11:53:17AM -, Simon Peyton-Jones wrote:
Your (1-Ross) ensures that every variable in the assertion does occur in
the head. But I'm not sure that the size-reduction argument is
watertight in the
| Yes, (1-GHC) certainly contradicts the FD paper that Martin and I
wrote.
| I think (1) should be:
|
| (1-fixed) Each assertion in the context must constrain type
| variables, and
| those type variables must all be mentioned in the head.
|
| That is, there is no requirement that the
I have not followed this completely, but do these new rules now allow:
class F a b c where
f: a - b - c
and then
instance F a a a where
...
which gives currenly gives (using -fglasgow-exts):
Test.hs:6:0:
Illegal instance declaration for `F a a a'
(There must be at least one
On Mon, Feb 06, 2006 at 01:53:17PM +0100, Doaitse Swierstra wrote:
I have not followed this completely, but do these new rules now allow:
class F a b c where
f: a - b - c
and then
instance F a a a where
Yes. Indeed they allow any unconstrained instance. They would
also allow
| I have not followed this completely, but do these new rules now allow:
|
| class F a b c where
|f: a - b - c
|
| instance F a a a where
Ross's proposal would allow that.
Ignore functional dependencies for the moment. To force instance
inference to terminate we need the context of the
I took a look. Here's a typical example:
newVariableListFromSet :: Ord a = VariableSetSource a - VariableList a
newVariableListFromSet (variableSetSource :: VariableSetSource a) =
let
attachListOp parallelX (listDrawer :: ListDrawer a pos) =
do
(posRegistry ::
Simon Peyton-Jones wrote:
I took a look. Here's a typical example:
newVariableListFromSet :: Ord a = VariableSetSource a - VariableList a
newVariableListFromSet (variableSetSource :: VariableSetSource a) =
let
attachListOp parallelX (listDrawer :: ListDrawer a pos) =
do
| That was exactly my problem. How should I find out the type of
| attachListOp (I have not written this bit of code)? Could I somehow
ask
| ghci-6.4.1 to do it for me?
(Unsatisfactory but would work) You could compile with -ddump-ds and
look at the output.
Simon
Bulat Ziganshin wrote:
Hello ,
yes, i found this famous -c bug! the humor of situation is what
easiest way to got this bug is to run ghc itself! :) it seems that
noone except me tried this ever. i just found that any large enough
module raises this error!!! that, for example, results of
Simon Peyton-Jones wrote:
(Unsatisfactory but would work) You could compile with -ddump-ds and
look at the output.
Yes, I did work (for VariableList.hs)
attachListOp :: forall pos . ParallelExec - ListDrawer a pos
- IO (IO ())
Thanks, Christian
(I need to get a new ghc-6.5 without the
Hello Ross,
Monday, February 06, 2006, 2:35:40 PM, you wrote:
RP A patch implementing a relaxed termination constraint is at
RP http://www.soi.city.ac.uk/~ross/instance-termination.patch
[this patch provides the following:]
RP With -fglasgow-exts but not -fallow-undecidable-instances
Hello GHC,
Monday, February 06, 2006, 7:59:24 PM, you wrote:
G #649: class declaration accepts conop as method name
G Type: bug | Status: closed
G Fixed in HEAD but wont't fix in 6.4.2
why you are not fixing this bug in 6.4.2? imho, we need to have more
stable GHC
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